In the utilization, extraction, storing, and regulation of fluids such as water and petroleum, it is important to know the parameter that determines the quantitative output. The same applies to the lowering of ground water for purposes of draining, to the obtention of geothermic heat by means of water, and to related problems.
The quantitative output is proportional to the transmissibility of the fluid-conducting layer of earth.
The invention involves a method for the determination of the transmissibility in a fluid-conducting stratum especially an aquifer.
The transmissibility T is expressed by EQU T=k.multidot.d
which has the dimensions of m.sup.2 /s (meters squared per second)
with k=permeability =length/viscosity=m/s and, PA1 d=thickness of the stratum (m).
The usual methods to determine the transmissibility of an aquifer are based on the evaluation of pumping tests. Less often injection tests are in use for this purpose.
For performing a pumping test, usually a pumping well and several observation pipes are drilled into the fluid-conducting layer. Then the fluid is pumped out for some time with a constant discharge. Thereby the water level in the pumping well and the observation pipes is lowered. From the lowering and/or resurgences in relation to space, time and the discharge, the transmissibility and the permeability are calculated.
Other possibilities for determining the transmissibility reside in introducing fluid into the formation that is to be examined. This may be done at a constant rate, with sudden changes, or periodically (U.S. Pat. No. 3,559,476). The flow or the change in pressure in the head of fluid is measured in the well itself or in adjacent boreholes (German Auslegeschrift 1,289,803).
Pumping tests are expensive and time consuming. Frequently they are difficult to carry out technically and present a problem in the disposal of the water that has been pumped out. Injection tests present similar problems. Here the technical execution, including the delivery of the fluid, the preparation of the wells, and the measurements themselves, are likewise expensive and time consuming.
It is the aim of the invention to avoid the high costs and technical difficulties of the pumping and injection tests and to measure directly from one borehole of small dimensions, the transmissibility of the surrounding stratum quickly and at lesser costs.
In addition to the different measuring principles, the chief differences between the present invention and the pressure measuring device of German Auslegeschrift 1,108,154 lie in the fact that the pressure measuring probe is equipped with a pressure compensating vessel disposed outside of the fluid in the air-filled portion of the well. This produces a compensation of the atmospheric pressure or the applied compressed air so that the movement of the surface of the water is measured.